When you've built up equity in your home this type of loan becomes available to you.
It works like this - once you've paid off some of your mortgage and/or the property has risen in value, you can borrow against that equity for other investments.
For example, you can borrow for renovations such as a new bathroom, kitchen or home extension, or you can buy another property, or invest in shares, or jet away on a special holiday.
A Home Equity Mortgage simply allows you to access the value in your home to do other things.